Abstract: A swinging bucket centrifuge rotor having a plurality of cavities spaced about its vertical axis and extending entirely through the rotor. Each cavity is adapted to receive a bucket supported by a hanger rod. The mounting of the bucket is such that the bucket can pivot or swing from a vertical to a horizontal position during operation. Each cavity is provided with a slot, which extends along the underside of the rotor, from the cavity to the periphery of the rotor. The slot has an upper surface adapted to receive the bucket when the bucket is in the horizontal position. A pair of opposed grooves extend partway down the wall of the cavity whereby the ends of the grooves each form a ledge to support an end of the hanger rod by which the bucket is pivotally suspended.